Various laser manipulators and robots conducting laser operations, such as welding, cutting of a workpiece, and deburring of cast and molded products by the use of a laser beam, through manipulated and robotic motions of the robots, are conventionally well known. The conventional manipulator for a laser operation is a gantry type laser machine provided with a gantry-shape machine framework, and a laser emitting unit supported by the gantry type machine framework to be moved along two orthogonal axes in a plane and along an axis perpendicular to the plane, and is effectively used for laser emitted operations such as a welding of a flat shape workpiece.
The conventional laser robot is a cartesian coordinate robot provided with a robot mechanism to move a laser unit for collecting a laser beam introduced from a laser source through an appropriate laser beam conduit, in two orthogonal axis directions and another axis direction vertical to the two orthogonal axis directions, to thereby conduct a laser operation such as a welding on a surface of a workpiece. The former and latter laser manipulator and laser robot are able to advantageously conduct an accurate laser operation on a flat workpiece by a detection of a position on the surface of the workpiece by a distance sensor, but it is difficult or impossible for both the manipulator and the robot to bring a front end of the laser collecting and emitting unit toward a corner or corners of a complicated three-dimensional article. Furthermore, in the case of the laser manipulator, the laser operation must be conducted on a workpiece mounted on a worktable disposed inside the robust gantry-shape framework, and therefore, it is difficult to install the laser manipulator in the production line of a factory, and thus the laser manipulator has a disadvantage in that it must be installed and used at a position away from the production line.
On the other hand, in the case of the laser robot, specifically a multi-articulation laser robot, the laser collecting and emitting unit attached to an end of the robot, i.e., a robot wrist, is able to access corners of a complicated three-dimensional article or product to thereby conduct a desired laser operation by the laser emission, due to the maneuverability of the robot about respective articulations, and therefore, is able to overcome the above-mentioned disadvantage of the gantry type laser manipulator.
Nevertheless, the multi-articulation type laser robot has a motion mechnism such that an end effector of the robot, to which the laser collecting and emitting unit is attached, must be brought to a target position by total changes in the position and attitude of respective movable elements of the robot, which changes are caused by rotating the respective movable elements about a plurality of articulations thereof. Therefore, when the laser operations are conducted in a continuous manner, as the laser emitting end of the laser collecting and emitting unit must be kept at a constant distance from the surface of a workpiece, it is very difficult for the robot to accurately position the end effector and the laser collecting and emitting unit each time at each position adjacent to each desired position on the surface of a workpiece, to thereby apply a laser beam to the desired position, because during the moving of the movable elements of the robot, small delays in the motions about respective articualtions are gradually accumulated to cause an error in the abovementioned positioning of the laser collecting and emitting unit. Accordingly, even if the known precise light sensitive type distance detector is employed to accurately detect a distance between the laser emitting end of the laser collecting and emitting unit and the surface of the workpiece, the robot per se cannot move rapidly enough to permit the laser emitting unit to emit a laser beam in accordance with the detected data of the light sensitive type distance detector, and accordingly, it is impossible to expect an accurate laser operation by the laser robot. Further, when a compensation for an error between an actual distance between the laser emitting unit and the desired position on the surface of the workpiece and the detected data of the light sensitive type distance detector is conducted, the respective movable elements of the robot must quickly start a compensating motion thereof about respective articulations to achieve a real time compensation. Each of the movable elements of the robot, i.e., a swivel body, and each robot arm, however, has such a large moment of inertia that the motion of the element cannot be quickly started, and therefore, the speed of starting of the motion of the each element cannot be faster than a given limited speed, and thus the robot cannot carry out a complete compensating motion due to a delay in the start of the motion of the robot. Consequently, the conventional multi-articulation type laser robot cannot be used for an accurate laser operation, for example, a cutting of a semiconductor wafer.